| 摘要 |
PROBLEM TO BE SOLVED: To shorten the length of piping of an exhaust system to reduce costs and improve operating efficiencies by preparing a molded item of fibers having ionic radicals of specific quantities, which exhibit, in a single or composite form, water absorption properties and moisture absorption properties, so as to have a specific density. SOLUTION: When a low-density filter element for rapidly capturing substances in the form of gas, mist, and dust discharged from a vacuum exhaust system of semiconductor manufacturing process is manufactured, a moisture of 0.5-70 wt.% is given to a mixture containing fibers which exhibit, in the form of single fiber or fibers of various kinds, water and moisture absorption properties and which have ionic radicals of 0.1-0.8 mmol/g in total amount. The surfaces of the fibers are partially gelled and the fibers are then put into a molding machine and dried by blowing into the machine a hot air at a temperature of 30 deg.C or higher and 250 deg.C or lower. Thus, the maintenance of the exhaust system can be facilitated and hence costs to be born by a user can be reduced. The density of the filter is 0.005-0.4 g/cm3, preferably 0.01-0.4 g/cm3, more preferabley 0.03-0.1 g/cm3.
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